Breech bolt for firearms



Aug. 12, 194.7.

' 2 Shets-Sheet 1' ventor I L.

Blv

Attorney;

Aug. 12, 1947. G. w. PATCHETT 2,425,634

BREECH BOLT FOR FIREARMS Fil ed Feb. 7, 1944 2 Sheets-Sheet 2 l (PInUeTI O a y L raw- Attorney Patented Aug. 12, 1947 UNITED STATES Application February 7, 1944, Serial No. 521,402 In Great Britain October 25, 1943 4 Claims.

This invention relates to improvements in connection with firearms and has more particular reference to breech blocks or bolts used in such arms, and finds particular use in automatic weapons, that fill a military necessity between the rifle and the pistol. In such weapons the breech block or bolt, hereinafter referred to as the bolt, with its firing pin explodes the cartridge, provides the abutment for reaction of the exploded charge and in turn and under recoil moves rearward in the bolt race against resilient pressure to repeat or be latent to repeat the same operation again. It follows that unrestricted movement in its race is essential for operation, and, Whilst such movement may be prevented in design by a sear under manual or selective control, adventitious material such as sand, mud or dirt can also provide a total impediment to movement, particularly when the arm is used in desert warfare or when the weapon has been in contact with mud, dust, sea water, or exposed to tropical rain or mist. The entry of adventitious material to the bolt race is facilitated by direct openings or passages thereto. Thus, the axial slot of the cocking device, the aperture of the ejection orifice and the magazine mouthpiece itself all communicate with the bolt race. Additionally, the trigger seldom has a dust-tight arc of movement, and sand in a sand storm will penetrate at any opening however minute, and all such matters tend to detract from the readiness or reliability of the weapon to operate at instant call.

The object of the present invention is to overcome these difficulties and to render the bolt selfclearing in its backward and forward movement and to provide a positive tendency to eject any adventitious lodgment.

The invention consists in the combination with a bolt as employed in firearms of the types set forth of raised bearing surfaces or lands formed upon the said bolt and adapted to engage upon their outer surfaces with the inner surface of said bolt race, said lands having pointed or like extremities formed to clear a gritless surface for subsequent continuous or other movement.

The said lands are arranged helically on the periphery of the bolt, and are provided with pointed or plough-shaped extremities, fore and aft. The number of said bearing surfaces or their width may vary, and to prevent undue wear, and for other reasons more fully set out hereafter, the lands are formed as a helix upon the bolts longitudinal circumference, or right or left handed helical lands may be used so that any tendency for the bolt to have angular movement as with a ATENT oFFicE helical land of unidirectional pitch, may be avoided.

Since the movement of any bolt with helical lands will expose the land edges to the axial cocking lever slot or the like, impurities will tend "to be ejected. In less positive degree foreign matter displaced by reciprocation of a bolt with the sharp nosed axial bolt lands is also ejected through one or other, or all, of the several openings or passages in the bolt race.

In order that the invention may be more fully and particularly described, reference is made to the accompanying drawings wherein the inventionis illustrated as applied to a known type of automatic firearm, and wherein Fig. 1 is a longitudinal section of a bolt and a bolt race, showing one form of the invention.

Fig. 2 is a section on the line 2-2 in Fig. 1.

Fig. 3 is an elevation of a bolt with two-start helical lands.

Fig. 4 is an end view of Fig. 3.

Fig. 5 is an elevation of a bolt with two-start reversed helical land.

Fig. 6 is an end view of Fig. 5.

Fig. 7 is an elevation of a bolt having four lands arranged helically so that their ends are in line or overlap the opposite end of the adjoining land.

Fig. 8 is an end view of Fig. 7.

In the drawings the bolt i may be of any required pattern; it may be pertinent to rifles or to automatic arms. The particular form shown is suitable for automatic weapons and is given by way of illustration only.

Referring to Figs. 1, 2, 7 and 8, the raised bearing surfaces or lands 2 are formed or applied helically to the axis of the bolt I, and leave spaces 3 intermediate between the bolt body perimeter 4 and the bolt race or casing 5 (see Figs. 1 and 2). The spaces 3 are made sufficiently large for unwanted intruding matter to have free movement, with opportunity, under disturbance, of escape through the slot 6 (see Fig. 1) of cocking lever I fixed to the bolt (see Fig. 2) or other opening communicating with the bolt race. The extremities 8 of the said lands or raised portions may be curved from both sides as shown at 8 in Fig. '7, or be of coned appearance, or chisel shaped as shown at 82 in Figs. 3 and 5, to provide a contour for shearing and clearing, for instance, dried mud from the bolt race In.

Figs. 3 to 8 inclusive show the raised surfaces or lands helically cut on the bolt periphery. This arrangement provides for cylindrical wear of the bolt race, and equally assists in quickly conveying unwanted matter to the longitudinal opening 6. If helical lands of unidirectional pitch are employed as shown at 2 in Figs. 7 and 8 or at 22 in Figs. 3 and 4, the compression spring l2 may be wound to resist any tendency of the bolt to turn about its axis or press the cooking lever 1 upon the upper or lower edge of the slot 6. Should in some arms this prove diificult, then two-start right and left handed helical lands 2b (Fig. may be formed upon the bolt periphery, gaps I I, (Fig. 5) being cut at the crossings for matter otherwise wedged in to escape.

In operation and whether the bolt is cocked or not, movement of said bolt by recoil, spring or hand manipulation, clears by a shearing action the bolt race face I!) of adherent or loose adventitious matter, which, being disturbed, is then free to escape from the opening whereby it entered or any other opening available.

It is found that weapons not constructed in accordance with this invention, and which have been immersed in mud, when warm, will fail, since the heat of the weapon solidifies the earth matter on the surface of the bolt race. By means of the prevent invention, however, a clean path is out by the initial longitudinal movement of the bolt, rendering subsequent movement a certainty.

I claim:

l. A firearm comprising, in combination, a bolt race having a longitudinally continuous interior surface and a longitudinal slot in a side and open to the exterior thereof, and a breech bolt reciprocable longitudinally in said race and having a cooking handle connected thereto and extending through said slot to the exterior of the race, the breech bolt having lands extending helically on and projecting from its periphery and providing peripheral bearing surfaces which slidably engage the interior surface of the bolt race to support the breech bolt therein and clear foreign matter from said surface, said lands providing a space between them to receive foreign matter cleared from said interior surface and communicating with said slot in the bolt race for conveyance of such foreign matter thereto.

2. Afirearm as defined in claim 1, wherein said helical lands have unidirectional pitch along the periphery of said breech bolt, and said cocking handle engaging in said slot in said bolt race prevents rotation of said bolt in said race.

3. A firearm as defined in claim 1, wherein said helical lands have respectively relatively reverse pitches along the periphery of said breech bolt, and have ends which are spaced apart to leave openings between them.

4. A firearm as defined in claim 1, wherein said helical lands are arranged in a pair and are respectively at diametrically opposite sides of the periphery of said breech bolt.

GEORGE WILLIAM PATCHETT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,083,384 Browning Jan. 6, 1914 1,586,048 Schmeisser May 25, 1926 2,049,776 Hyde Aug. 4, 1936 2,096,028 Burton et al Oct. 19, 1937 1,291,689 Sheppard Jan. 14, 1919 1,470,029 Pedersen Oct. 9, 1923 

